Process for the treatment of ores containing antimony.



UNITED STATES PATENT OFFICE.

Specification of Letters Patent.

Patented Aug. 8, 1905.

Application filed April 15, 1905; Serial No. 255.828.

To all whom it may concern.-

Be it known that I, JOHN STEWART MAoAR- THUR, a subject of the King of Great Britain and Ireland, and a resident of Glasgow, Scotland, (whose postal address is 74 York street, Glasgow, Scotland,) have invented a certain new and useful Improved Process for the Treatment of Ores Containing Antimony, of which the following is a specification.

This invention has for its object the removal of antimon compounds from ores containing them, 'sp ecially stibnite,) the recovery of the antimony compounds, and the regeneration of the chemicals employed.

In carrying out the invention the crushed ore is treated with an aqueous solution of a fixed alkali. It has been found in practice that this solution must not exceed four per cent. of caustic soda or its equivalent of other alkali (and unless the ore contain oxid of antimony it should not exceed two per cent.,) for if it be stronger then the silica of the ore is more liable to be attacked and also the amount of antimony compounds taken into solution is so great that an unmanageable thick sludge may be formed upon its precipitation later. During the treatment of the ore the alkaline solution is maintained at a temperature which need not exceed its boilingpointsay at about 100 centigrade-and may advantageously be maintained'at about that temperature (and in any case should not be allowed to fall below 50) until certain subsequent operations, as, if the temperature be allowed to fall, a proportion of the antimony compounds taken into solution may be precipitated, and thus choke pipes or other parts of the apparatus.

By treatment with the alkali solution the antimonial content of the ore is dissolved. The antimony compound contained in it is then precipitated as a sulfid (or equivalent compound'depending upon the nature of the ore) by treatment with a suitable acid, preferably, for-the reasons hereinafter stated, carbonicacid gas. The salt remaining in solution is then regenerated.

Although the apparatus employed forms no part of my invention, I refer to known devices, utensils, and plants of various kinds in the following exemplary exposition of the improved process merelyfor the sake of rendering the description clear and easily followed.

Preferably on the score of cheapness the alkali employed is caustic soda and the solution of it used, as hereinbefore stated, of a determinate strength not exceeding four, and

preferably about two, per cent. This solution is prepared in a causticising-vat provided with an agitator and a steam jacket or coil and is delivered therefrom to a storage vat, also provided with a steam jacket or coil, in which its temperature is maintained at about 100 centigrade. The heated solution is then led to extraction-vats (of which thereare preferably two) provided with agitators, and it may be with steam jackets or coils.

The antimonial ore in a state of comparatively fine division-such, say, as to pass through a sieve of twenty meshes per lineal inch-is introduced into the extraction-vats, and the heated alkali solution is then allowed to act upon it, either at one or iii successive operations, taking into solution practically its whole antimonial contents, when the quantity of antimonial compound, if stibnite, does not exceed twice the quantity of caustic soda or equivalent. The solution with any remanent insoluble matter is then discharged from the extraction-vats through a monte-j us or other pumping apparatus to a filter-press,

the efliuent from which passes to precipitation-vats. In the precipitation-vats the antimony is precipitated from the solution and carbonate of soda formed in it by carbonicacid gas passed into the solution bydistributing devices, the carbonic-acid gas being preferably obtained from lime-kiln or furnace gases. Preferably the solution is cooled while in the precipitation-vats in order that the precipitation of its antimony content may be more rapid and complete. This cooling may be achieved naturally or artificiallyfor ex-v ample, by passing cold water through pipecoils in the vats or through jackets surrounding them. The antimonial magma from the precipitation-vats is discharged to a filterpress, the effluent carbonate-of-soda solution from which is delivered to sumps, while the recovered antimony compound is removed from the filter-press in the usual cake form. The cabonate-of-soda solution is delivered from the sumps back to the causticising-vat (and may be led through an evaporator on the way for the purpose of concentrating it) and caustic soda is re-formed by a suitable causticiser, preferably lime obtained from the kiln supplying the carbonic-acid gas, economy being thus attained. The process thus proceeds in a cycle, the alkaline solution first acting on the ore then being formed into a carbonate and then recaustieised repeatedly.

I am aware that it has heretofore been proposed to treat antimonial ore with a fixed alkali, a fixed alkaline sulfid, or a sulfid of the metal of an alkaline earth in order to dissolve its antimonial content and to subsequently precipitate the antimonial compound by means of an acid, such as hydrochloric; but essential features of my improved process are, first, the use of the specific reagents mentioned, which, contrary to those hitherto proposed or used, are such that the regeneration of the dissolvent is conveniently possible and that the process is commercially feasible, and, secondly, the strength of the dissolvent and the temperature at which it is used and which it exceeded in the first case or not maintained in the second completely abrogate the commercial value of the process.

WVhat I claim is 1. A process for the treatment of ores containing antimony consisting in, firstly, treating the ore with a solution containing not more than four per cent. of caustic soda the solution being meanwhile maintained at atemperature exceeding 50 centigrade whereby its antimonial content is dissolved; secondly, precipitating, by carbonic-acid gas, the antimony from the antimonial solution thus obtained and forming at the same time carbon ate of soda therein; and, thirdly, regenerating the alkali solution by treatment with lime,

. as described.

2. A process for the treatment of ores containing antimony consisting in, firstly, treat- -ing the ore with a solution of a fixed alkali of a causticity equivalent to not more than four per cent. of caustic soda the solution being meanwhile maintained at a temperature exceeding 50 centigrade whereby its antimonial content is dissolved, secondly, precipitating, by carbonic-acid gas, the antimony from the antimonial solution thus obtained and forming at the same time an alkaline carbonate therein; and, thirdly, regenerating the alkali solution by treatment with lime, as described.

3. A process for the treatment of ores containing antimony consisting in, firstly, treating the ore with a solution of afixed alkali the solution being meanwhile maintained at a temperature exceeding 50 centigrade whereby its antimonial content is dissolved; secondly, precipitating, by carbonic-acid gas, the antimony from the antimonial solution thus obtained and forming at the same time an alkaline carbonate therein; and thirdly, regencrating the alkali solution by treatment with lime, as described.

A. A process for the treatment of ores containing antimony consisting in, firstly, treating the ore with a solution of a fixed alkali the solution being meanwhile maintained at a temperature exceeding 50 centigrade whereby its antimonial content is dissolved; secondly, precipitating, by carbonic-acid gas, the antimony from the antimonial solution thus obtained and forming at the same time an alkaline carbonate therein; and thirdly, regenerating the alkali solution, as described.

5. A process for the treatment of ores containing antimony consisting in, firstly, treatingthe ore with a solution of a fixed alkali of a causticity equivalent to not more than four per cent. of caustic soda the solution being meanwhile maintained at a temperature exceeding 5O centigrade whereby its an timonial content is dissolved, secondly, precipitating, by carbonic-acid gas, the antimony from the antimonial solution thus obtained and forming at the same time an alkaline carbonate therein; and, thirdly, regenerating the alkali solution, as described.

6. A process for the treatment of ores containing antimony consisting in, firstly, treating the ore with a solution of a fixed alkali of a causticity equivalent to not more than four per cent. of caustic soda the solution being meanwhile maintained at a temperature exceeding 5O centigrade whereby its antimonial content is dissolved; secondly, precipitating the antimony from the antimonial solution thus obtained; and, thirdly, regenerating the remanent solution, as described.

7. A process for the treatment of ores containing antimony consisting in, firstly, treating the ore with a solution of a fixed alkali the solution being meanwhile maintained at a temperature exceeding 50 centigrade whereby its antimonial content is dissolved; secondly, precipitating the antimony from the antimonial solution thus obtained; and thirdly, regenerating the remanent solution, as described.

in testimony whereof I have signed my name to this specification in the presence of two subscribing witnesses.

JOHN STEWART MACAR'IHUR.

WVitnesses:

WILFRED HUNT, JAMES EAGLESOM. 

